Adsorption of Indigo Carmine Dye by Composite Activated Carbons Prepared from Plastic Waste (PET) and Banana Pseudo Stem

This study is on the adsorption of indigo carmine dye by composite activated carbons prepared from banana pseudo stems and plastic waste. The activated carbons named TB1P1, TB1P1h and TB2P1 were obtained by pyrolysis at 700°C under steam of raw materials at different ratios (1:1 and 2:1). They were characterized by different techniques such as SEM/EDX, Raman Spectroscopy, FTIR, XRD, TGA/DTA and BET/BJH. Analyses indicate amorphous structures with specific surface areas of 424.37;385.45 and 338.84 m2/g for TB1P1, TB1P1h and TB2P1 respectively. The study of the adsorption of indigo carmine dye by these adsorbents was carried out by varying parameters such as contact time, mass of adsorbent and initial concentration of the dye. The maximum retention is 94.71%, 86.18% and 84.17% for TB1P1, TB1P1h and TB2P1 respectively after 60 min of stirring, for a pH = 4.6 using 0.6 g of adsorbents. The adsorption of indigo carmine follows well, the Langmuir model, with the most suitable kinetics as pseudo second order.

Bioefficacy of Plectranthus kirbii Powder and Extracts on Stored Cowpea Pest Callosobruchus maculatus (Coleoptera: Chrysomelidae)

Cowpea seed constitutes an important source of proteins for populations in Sub-Saharan Africa. But this food resource is heavily damaged by cowpea beetle Callosobruchus maculatus. The control of that pest is mainly carried out by using synthetic insecticides. Despite the efficacy of this method, it caused environmental and health problems. Therefore, the search for alternative methods is vivaciously needed. In this issue, the bio-efficacy of Plectranthus kirbii extracts was assessed on C. maculatus regarding adult mortality, suppression of population and grain damage as well as seed viability preservation and repellency. The leaf powder and aqueous extracts of the plant were tested at 2, 4, 8 and 16 g/kg on bruchid adult for toxicity and damage bioassays. Repellency test was carried out using the plant aqueous, methanolic and ethyl acetate extracts at 0.5, 1, 2 and 4 mg/cm2. The seed viability was evaluated using seeds preserved for three months at the single concentration of 16 g/kg of each plant extract. Significant mortality of cowpea beetle was induced by the plant aqueous extract and leaf powder. LC50 values decreased with the increasing exposure period, and aqueous extract and leaf powder recorded 33.42 and 9.48 g/kg respectively within 3 days whereas within 5 days, the same extracts in the same order recorded LC50 of 1.31 and 8.73 g/kg respectively. These extracts significantly reduced damage by suppressing almost completely the bruchid population growth. The non-infested grain preserved recorded high grain viability compared to the infested ones. The non-treated infested recorded the lowest germination rate (11.33%). The repellency rate ranged from 38.75% to 83.75%. Ethyl acetate and methanolic extracts were classified as the class III repellent product, while aqueous extract ranged as class IV in repellency. Considering these findings, the extracts of P. kirbii could favourably replace the synthetic insecticides used in the cowpea protection during storage.

Preparation and Characterization of Magnetic Banana Peels Biochar for Fenton Degradation of Methylene Blue

Co-precipitation method was used for the synthesis of biochar/Fe3O4 to heterogeneously degrade methylene blue (MB) in an aqueous medium. This catalyst was characterized by different techniques such as Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Raman Microscopy. The analysis highlighted the presence of iron oxides on the surface of the biochar in the form of magnetite (Fe3O4). Catalytic tests performed on this composite showed significant degradation and simple magnetic separation in the solution for reuse. Maximum degradation was carried out after stirring it for 90 minutes in an MB aqueous solution at different concentrations. The percentages of degradation were 99% and 98.6% 93.3% and 91% for concentrations of MB 40 mg/L and 60 mg/L, 80 mg/L and 120 mg/L respectively. The reactions followed a second-order kinetics with correlation coefficients r2 = 0.9598, 0.9247, 0.9548 and 0.9614 for the same concentrations of MB at pH = 2, 0.2 mL/L H2O2 and 15 mg of biochar/Fe3O4. This work provides a simple and an effective method for the preparation of biochar/Fe3O4 and its use for the oxidation of MB by means of heterogeneous Fenton.

Mining Implication in the Geochemical Exploration of Fluvial Sediments of the East Nyambaka Volcanic Zone (Adamawa-Cameroon)

Geochemical characterization in stream sediments from Nyambaka locality was carried out on ten samples collected from the study area watershed. The distribution of trace metals in the sediments showed that some lithophiles (Be, Sc, V, Cr, Sr, Th, U), chalcophiles (Cu, Zn, Ga, As) and siderophiles (Mn, Co, Ni, Mo) have high average contents in the sediments compared to their average concentration in the upper crust. From the factorial analysis of the components, the total variance explained made it possible to represent and capture the main information on the data and to represent them in a graphical frame. Thus, using this graphical frame, the trace elements were divided into four groups opposed to each other. They show an enrichment of stream sediments in group 1 (Cr, Cu, Mn, Be, Ni, Co, Zr, Sr, Ba, Mg) and group 2 (Mo, As, Hg, V, Ag) elements more than group 3 (Ga, Sc, U) and group 4 (Au, Th). Rare earth analysis indicates a high abundance of Lanthanide (28.1 ppm to 42.4 ppm), a high concentration of light rare earth (LREE), and depletion of heavy rare earth (HREE). The variable LREE/HREE (7.24 LREE/ HREE 12.22) and (La/Yb)N (6.70 (La/Yb)N 11.72) ratios suggest an effect of heterogeneous sorting of heavy minerals with variable enrichment of dense and resistant minerals.

A Novel Hybrid MPPT for Wind Energy Conversion Systems Operating under Low Variations in Wind Speed

This manuscript presents a new approach MPPT (Maximum Power Point Tracking) for improving and optimizing the performance of a Wind Energy Conversion System (WECS) operating for small variations in wind speed by combining sliding mode control and fuzzy logic control. The proposed method consists of optimizing the sliding mode controller by the fuzzy controller. The main purpose of the Sliding Mode control-Fuzzy Logic controller (SM-FL) is to ensure the robustness (by eliminating certain disadvantages of the sliding mode control such as the phenomenon of chattering) and the stability of the control system in the case of small variations in conditions atmospheric (here variation of the wind). Our system consists of a wind turbine, a Permanent Magnet Synchronous Generator (PMSG) and a DC-DC boost converter connected to a continuous load. The performances of the method suggested are compared with those of fuzzy logic and fuzzy-Proportional Integral (FL-PI) in term speed of convergence, of tracking time and tracking efficiency. The results of numerical simulation of our system confirmed the best performance of this method.